1,720,989 research outputs found
Metal additive manufacturing at infn_lngs laboratory: facilities, testing and future capabilities
No full textINFN “Gran Sasso National Laboratory” (Laboratori Nazionali del Gran Sasso - LNGS) is the largest
underground laboratory in the world devoted to neutrino and astroparticle physics. Internally, the Mechanics service is
focused on design and manufacturing of complex devices for both nuclear and astroparticle physics research and
industrial technology transfer. Among its activities there are: traditional and CNC machining, quality control, mechanical
design, multi-physics simulations, reverse engineering, and Additive Manufacturing (AM) both for plastic and metallic
materials. In the INFN context, it poses itself as a reference for Additive Manufacturing (AM), quality analysis and
chemical characterization. Intense activities, often in collaboration with other international laboratories, universities, and
industries, are ongoing in this field. The service is equipped with an L-PBF machine, based on the Selective Laser
Melting (SLM) technology. Materials such as Copper (e.g., OFHC / 99.8%), Copper alloy (e.g., CuCrZr), Steel alloys
(e.g., AISI 316L) and Aluminum alloys (e.g., SCALMALOY®) are currently used
Development of a wayside measurement system for the evaluation of wheel-rail lateral contact force
No full textConsidering the safety against derailment, it is essentially that a vehicle respects the force limits imposed by standards. This paper presents an experimental wayside measurement system for the measurement of the wheel-rail lateral contact force. While there are several well-known solutions for the monitoring of the vertical force, the measurement of the lateral one by means wayside systems is rather uncommon because of overlapping effects that are always present with vertical loads. The system, thanks to its particular sensors configuration, is instead able to isolate the strain effects of the vertical force from those of the lateral one. The research is based on laboratory tests, finite element simulations and on field test directly on a railway line in service. Besides, combining the system with another one for monitoring of the vertical force, it has shown the possibility to evaluate the derailment ratio for each train passing over the measurement site
Additively manufactured CuCrZr alloy: improvement of mechanical properties by heat treatment
Full text linkCuCrZr alloy plays a fundamental role for the production of critical components because it is characterized by good thermal and electrical conductivity and by high mechanical strength after precipitation hardening treatment. In the framework of a wider research on the mechanical behaviour of additively manufactured CuCrZr alloy, this study focuses on the effects of heat treatment parameters on the alloy strength. The additive manufacturing process, characterized by very high cooling rates, determines the formation, in the as-built condition, of a supersaturated solid solution. The results obtained reveal that aging temperature and time are critical parameters for improving the mechanical behaviour of CuCrZr alloy which behaves differently than the alloy produced through the use of traditional techniques
Experimental Data Collection of Surface Quality Analysis of CuCrZr Specimens Manufactured with SLM Technology: Analysis of the Effects of Process Parameters
Full text linkSelective laser melting (SLM) is the most widely used laser powder-bed fusion (L-PBF) technology for the additive manufacturing (AM) of parts from metallic powders. The surface quality of the SLM parts is highly dependent on many factors and process parameters. These factors include the powder grain size, the layer thickness, and the building angle. This paper conducted an experimental analysis of the effects of SLM process parameters on the surface quality of CuCrZr cubic specimens. Thanks to its excellent thermal and mechanical properties, CrCrZr has become one of the most widely used materials in SLM technology. The specimens have been produced with different combinations of layer thickness, laser patterns, building angles, and scanning speed, keeping the energy density constant. The results show how different combinations of parameters affect the surface quality macroscopically (i.e., layer thickness, building angle, and scanning speed); in contrast, other parameters (i.e., laser pattern) do not seem to have any contributions. By varying these parameters within typical ranges of the AM machine used, variations in surface quality can be achieved from 10.4 μm up to 40.8 μm. These results represent an important basis for developing research activities that will further focus on implementing a mathematical/experimental model to help designers optimize the surface quality during the AM pre-processing phase
Strength and fatigue behavior assessment of the SCALMALLOY® material to functionally adapt the performance of L-PBF components within CAE simulations
No full textThanks to Laser Powder Bed Fusion (L-PBF) technology, SCALMALLOY® was the first aluminum powder material designed for Additive Manufacturing (AM), achieving a fine microstructure with high performance that is comparable to other cast materials. Despite the mechanical properties that can be achieved, there are some inherent factors that can impede components performance (i.e., surface roughness). Parts produced by L-PBF are usually characterized by rough “as-built” surfaces; hence, it is fundamental during the design phase to understand and consider how the quality of surfaces impacts on the part performance. This paper aims to provide a Computer-Aided Engineering (CAE) workflow to design components with different finishing regions in accordance with the functional distinction that exists among them. To achieve this goal, a comparison of the mechanical properties achieved for SCALMALLOY® specimens with and without post-processing is here assessed to fit proper material models for numerical simulation purposes. The material models, built with/from experimental data, are fit to functionally adapt the performance of 3D-printed objects inside CAE simulations like a Functionally Graded Material (FGM). A CAE design workflow is here applied to a case study, suitable to demonstrate how the methodology may support the integrated product–process design of structural parts reducing the cost of post-processing in AM. This approach may mitigate the performance decrease of “as-built” surfaces since the experimental results show a different fatigue endurance limit between the “as-built” and CNC machined specimens about of three times
Joining Dissimilar Steels by Means of Selective Laser Melting: Material Microstructure and Interfacial Characteristics
No full textThe increasing demand for designing complex structures using Functionally Graded Material boosts the research on reliable joining processes. For several industrial applications in the automotive, tooling, and petrochemical industries, the joining of a stainless steel with a low-alloy steel is often required to obtain a variation of mechanical and corrosion properties when different parts of the same structure are subjected to different working conditions. Welding a stainless steel with a low-alloy steel is a challenging operation because it is not easy to control the microstructure of the welded joint and to avoid metallurgical defects such as hot cracks. Moreover, traditional welding methods can only be applied to relatively simple geometries. To design and produce multi-material components, characterised by complex geometries, Selective Laser Melting process capabilities can be exploited. In this paper, an AISI 316L stainless steel is joined to 16MnCr5 steel by carefully tuning the process parameters. Metallurgical investigations coupled with Energy Dispersion Spectroscopy analyses allowed to evaluate the soundness of the joint and the effect of the process thermal cycle on the alloy microstructures and properties. The results are very promising and show that a careful selection of process parameters allows to obtain a continuous joint
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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